One teen is much older and needed a much more comprehensive kind of science learning. I sat down to compare the different kinds of curriculum at the beginning of this year after finding the choice we had made for Physical Science just didn't work out as well as we had hoped so after about 6-8 weeks of trying it out we then realized we needed to move on.
I found a schedule he can follow that sort of breaks things down into small chunks, which really helps because there is a great deal of information that is covered in each module.
You can also find more things to go along with this at Donna Young's site.
We also purchased Live and Learn's Lapbook/Notebook so that he can mix things up and do the On Your Own questions and Vocabulary in each module a bit different. He likes the change.
My younger teen is working Science Fusion "Diversity of Living Things". This program is an online, interactive text that has a workbook that goes along with it. He is also doing lapbooking with it. He is making his own folds as he goes along in the lessons.
Happy Science Learning!